The treatment of irritated, damaged and wounded skin remains a major health problem despite the development of numerous medications. Furthermore, a major need exists for skin-care products and medicaments in less-developed countries, particularly in the tropics, where conditions such as inadequate health care, widespread skin fungal diseases, and the use of flammables such as kerosene for cooking and similar conditions give rise to high incidences of skin injury. For such countries, there is a critical need is to produce effective medicines that can be produced at very low cost using readily available materials. Many approaches to wound-healing currently being developed, such as the production of growth factor proteins by recombinant DNA methods, the use of pharmaceutical drugs with wound healing attributes, and occlusive dressings for wounds, will remain beyond the economic reach of patients in these countries for the next few decades.
In more developed countries, increasing pressures for cost-containment in medical services also necessitate the development of low-cost products for skin care and pharmaceuticals for wound healing. Procedures such as hospitalization for the treatment of venous stasis ulcers, while therapeutically effective, are today rarely permitted by medical insurance providers and outpatient treatments are increasingly common. While many alternate therapies being developed, such as the use of growth factors to accelerate skin repair, these also promise to be relatively high cost therapies.
Delayed healing or incomplete healing in humans and other animals causes additional pain and suffering for the patient and markedly increases wound complications and medical costs, and often the wound continues as a chronic sore that requires extensive attention and medical care to control infection and tissue necrosis. Even when such wounds finally heal, the wound area is frequently devoid of the ability to respond to tactile stimulation and is often filled with excessive deposits of immature collagen that produces permanent scarring. The urgent need for improved wound-healing compositions also extends to wounds generated by surgical procedures. The success of surgical procedures, especially in very ill or elderly patients, is typically a function of the adequacy and speed of post-surgical healing.
Another aspect that can impair the normal healing response is excessive inflammation of injured or wounded skin. While the inflammatory process and its concomitant influx of white cells into the afflicted area are an integral part of the natural healing process, in some cases the inflammatory process becomes excessive and delays healing. The wounded tissue becomes locked in an early phase of the healing process and cannot proceed to completion. In such instances, compounds with anti-inflammatory activities are used to allow the process to proceed normally.
One promising approach for the therapeutic treatment of the clinical problems associated with inflammation and impaired wound healing has been the use of metal ions complexed to organic molecules or amino acids, amino acid derivatives and peptides. Some of these complexes possess anti-inflammatory activity, while others possess both anti-inflammatory activity and healing actions. Yet other complexes reportedly possess hair growth stimulating actions in addition to anti-inflammatory and/or healing activities.
The use of copper salts or complexes as anti-inflammatory agents for the healing of stomach ulcers in the treatment of patients suffering from acute or chronic arthritis dates back to the 1940's and 1950's (see, e.g., reviews by Sorenson, Inflammation 3:317-331 (1976); Agents and Actions 8:305-331 (1981), and Comprehensive Therapy 11:49-64 (1985)). The use of copper salts and complexes, such as copper-salicylate complex, seems to have been abandoned, apparently due to the early promise of the steroidal anti-inflammatories, such as hydrocortisone. Other complexes of copper with amino acids (tryptophan, lysine), with non-steroid anti-inflammatory drugs (indomethacin, ketoprofen, acetylsalicylic acid) or with fatty acids (oleic, lauric and caprylic acids) have been studied but, despite their promise, were rarely developed beyond the preclinical phases due to problems of irritation, toxicity, and inadequate efficacy.
While many copper-complexes have been reported to possess anti-inflammatory properties, a more limited group have been reported to also possess healing actions. Heintze (U.S. Pat. No. 4,123,511) reported that a copper oleate complex had anti-inflammatory and skin healing activity. Sorenson (U.S. Pat. No. 4,440,754) describes the use of complexes of copper(II) salts and amino acids, such as tryptophan or lysine, or with organic molecules such as 3,5-diisopropylsalicylic acid, acetylsalicylic acid or salicylic acid, to prevent and heal gastrointestinal ulcers. Using a wound-healing model, Townsend and Sorenson (Sorenson et al., Agents and Actions 8:305-325 (1981)) found salicylate-copper to accelerate the rate of healing and improve the quality of healing of surgically-induced ulcers in rats. Also, Sorenson writes (ibid. and Inflammation 3:317-331 (1976)) that Townsend demonstrated that copper(II)-(tryptophan).sub.2 increased the rate of ulcer healing in a surgically-induced ulcer model. The increased healing was purportedly due to a more rapid re-epithelialization of the wound and an increase in the quantity and quality of the collagen. Fine collagen fibers in a normal orientation developed in treated animals, in contrast to non-treated animals in which the new collagen was very dense and composed of thick, wavy disoriented bundles, resembling scar tissue.
Federici and Bertolotto (EP 450,398 and IT 9,019,948) reported that chondroitin sulfate-copper(II) complexes possessed anti-inflammatory activity. European Patent No. EP 66,283 discloses "eustatic" compositions which contain a non-toxic metal ion (including copper) and a glycosamino-glycan of hyaluronic acid or chondroitin sulfate useful as a cicatrizant (wound healing by closure).
UK Patent Application GB 2 044 265 describes metal complexes (including copper) of adenosine triphosphate as aiding the recovery of bone tissue in cases of fractures as well as in osteoporosis and bone cysts.
Konishi (U.S. Pat. No. 4,461,724) reports that the tetrapeptide Gly-Ser-His-Lys and peptides of related structures possess anti-inflammatory and healing actions when complexed with metals such as ionic copper and zinc.
Yu (U.S. Patent 4,053,630) discloses the use of cysteic acid and its derivatives cysteine sulfinic acid or homocysteic acid, chelated to metal ions such as ferric, cupric, zinc or aluminum, to form compositions that alleviate symptoms of diseases characterized by defects of keratinization and achieved a remission of ichthyosis, dandruff and acne. Bertelli (U.S. Pat. No. 4,156,737) suggests that copper complexes of p-aminomethyl-benzene-sulfonamide possess healing and protective effects on skin burns. Van Scott (U.S. Pat. No. 4,283,386) teaches that metallic (copper, zinc, or aluminum) salt forms of cysteic acid, cysteine sulfinic acid and homocysteic acid have therapeutic actions that produce remissions of dry and broken skin, keratoses, warts and palmar and plantar hyperkeratosis.
Niwa (Dermatologica 179 S1: 101-106 (1989)) and Bergren et al. (Am. Surg. 54:333-336 (1988)) found that the anti-inflammatory protein Cu,Zn-superoxide dismutase also acts to enhance healing processes.
Pickart (PCT Publications WO 91/14437, WO 91/12267, WO 91/05797, WO 91/03488, WO 89/12441, WO 88/26448, WO 88/08851, EP Patents EP 190,736, EP 189,182; and U.S. Pat. No. 4,767,753) describes the synthesis and use of metal complexes of Gly-L-His-L-Lys as anti-inflammatory and healing agents.
A number of metal complexes have been used to promote hair growth. Yamashiki (Japan Pat. 70018997) used a complex of copper-pantothenate to purportedly promote growth of hair roots and promote skin functions. Morelle (U.K. Pat. GB 2097256, DE Pat. 32212448) used amino acid derivatives (N-butyryl amino acids) complexed with copper and other metals for cosmetic and therapeutic purposes, including use as hair and skin stimulants. Banfi et al. (U.S. Pat. No. 4,503,047) disclose a composition containing primarily one or more sulfur-containing amino acid(s) and copper(II) ions plus smaller amounts of allyl isothiocyanate and rhodanide ions to produce hair growth stimulating actions. Pickart (WO 91/07431, 88/08695 and EP 288,278) found a number of metal complexes of derivatives of Gly-L-His-L-Lys to increase hair follicle size and the rate of hair growth.
Despite the therapeutic promise of the above-mentioned metal complexes, toxicity and tissue irritation occur with many metal complexes (see, e.g., Johnson et al., Inorg. Chem. Acta 67:159-165 (1982); Pickart et al., Biochem. Pharm. 32:3868-3871 (1983); and Pickart et al., Lymphokines 8:425-446 (1983)). For example, while copper-salicylate complexes and numerous copper-salicylate analogs possess anti-inflammatory activities, other salicylate analogs such as the copper(II) complex of salicylaldehyde benzoyl hydrazone are highly toxic to tissues. Similarly, copper(II)-Gly-L-His-L-Lys supports cellular viability and possesses anti-inflammatory and healing actions, yet close synthetic aroylhydrazone analogs of its copper-binding region are extremely toxic to cells and tissues.
Another problem with copper complexes for therapeutic use concerns the binding affinity of copper ion to the complexing molecule. While a defined copper-complex can be synthesized, its therapeutic use places it in the physiological milieu of the tissues where a plethora of literally hundreds of compounds compete for binding to the copper ion, which can form electrostatic bonds to as many as six separate molecules. If the copper is removed from the complex and becomes loosely-bound, then tissue irritation occurs (see Raju et al., J. Natl. Cancer Inst. 69:1183-1188 (1982)).
Further complications arise when such metal complexes are formulated into carrier creams or ointments. Various chemicals are added to the formulations to increase adherence to skin and wound surfaces and to enhance the penetration of the complexes into the target tissue. Yet, since many of these substances also bind to the metals, the expected therapeutic benefits may be nullified or significantly attenuated. Also, detergents such as sodium dodecyl sulfate are used to help blend oil and water phases of the emulsions and stabilize the formulations. However, such detergents are themselves tissue irritants that can delay healing.
Another problem encountered with many of the metal complexes intended for therapeutic use is that they cannot be heat-sterilized; hence, to meet safety requirements, high concentrations of antimicrobial chemicals must be added during manufacture to inhibit the growth of microorganisms and the transmission of viruses. These antimicrobial agents may also inhibit the viability and function of a host's cells such as macrophages and fibroblasts that are involved in the maintenance and repair of skin and other tissue, and thus these agents may retard the healing response.
What are needed in the art are compositions useful in tissue protection, tissue healing, and/or stimulating hair growth, which compositions could be conveniently produced and at low cost. Preferably, the compositions could be sterilized without loss of bioactivity and could be formulated for topical application without the use of detergents or other potentially irritating compounds. Even more preferably, the compositions would be generally recognized as safe by regulatory agencies and thus could be used with minimal safety concerns and regulatory barriers. Quite surprisingly, the present invention fulfills these and other related needs.